JP5595892B2 - Single layer polyester film for photomask protective adhesive tape - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a photomask protective adhesive tape. More specifically, the present invention prevents internal foreign matters and agglomerated particles that can cause circuit defects, and efficiently performs a photoresist curing process. It is related with the polyester film which can be used.

  Conventionally, a photoresist having adhesiveness is used for manufacturing an electronic circuit board, and the resist is cured by irradiating ultraviolet rays around 360 nm through a negative film generally called a photomask.

  A polyester film having a thickness of 3 to 25 μm is used as a base material for the purpose of protecting the surface of the photomask for exposure used in close contact with the photoresist from damage and damage, and an adhesive layer is provided on one side of the base material. It is known to use a photomask protective tape having a release layer on its surface (Patent Document 1).

  Conditions such as having a high light transmittance as a photomask protective tape, having no change in adhesive properties due to ultraviolet rays, being able to be peeled off without leaving an adhesive on the photomask, and having a highly durable release layer Therefore, improvement of the release treatment layer, the release layer, etc. has been made so far (Patent Documents 2 and 3).

  In recent years, electronic circuit boards have become higher definition, and the width of wiring has been increased to about several tens of μm. For this reason, there is a problem that the internal foreign matter contained in the base film of the photomask protective tape impairs the light transmittance of the portion when irradiated with ultraviolet rays, the resolution is lowered, and a precise circuit pattern cannot be obtained.

  The main cause is antimony trioxide, which is a polymerization catalyst for the raw material polyester of the base polyester film, and if this is used in an added amount that allows a practical polymerization rate to be exhibited, the antimony trioxide is used during polycondensation. It has been pointed out that antimony oxide is reduced to form a metal antimony aggregate of about several tens of μm, and when a high-definition circuit pattern is formed, the transmission of ultraviolet rays is shielded to cause a defect in the circuit pattern.

  On the other hand, in the production of polyester film, in order to stabilize the appearance quality in the film winding process, silica, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride are used. In addition, fine particles such as aluminum oxide and kaolin are added to the film, but these particles also tend to form aggregates in the base film, and when forming a high-definition circuit pattern, ultraviolet rays are transmitted. There is a problem that the circuit pattern is defective. However, there is a problem that a film to which substantially no particles are added cannot be commercialized industrially because winding and handling are difficult.

JP-A-4-355759 Japanese Patent Laid-Open No. 9-230580 JP 2005-181564 A JP 2009-169351 A JP 2009-220284 A

  The present invention has been made in view of the above circumstances, and its solution is to reduce internal foreign matter, improve ultraviolet transmittance, and when used with a photomask protective adhesive tape used in a resist curing process. The object is to provide a polyester film capable of forming a fine circuit pattern.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by a film having a specific composition, and have completed the present invention.

  That is, the gist of the present invention is that the content of titanium element in the polyester film is 1 to 20 ppm, the content of phosphorus element is 1 to 300 ppm, the content of antimony element is 10 ppm or less, and the average particle size is 0.2 to 1. Photomask protection characterized by containing 0.01 to 0.15% by weight of crosslinked polymer particles having a particle size distribution of 0 to 0.1 μm and an ultraviolet transmittance of a wavelength of 360 nm of 84% or more. It exists in the single layer polyester film for tapes.

  According to the polyester film of the present invention, it is possible to reduce internal foreign matter, improve the ultraviolet transmittance, and form a high-definition circuit pattern when used as a photomask protective adhesive tape used in a resist curing process. , Its industrial value is great.

  The polyester film of the present invention is characterized by containing both a titanium compound and a phosphorus compound. That is, the titanium element content in the polyester film of the present invention needs to be 1 to 20 ppm, preferably 1 to 10 ppm, and more preferably 1 to 15 ppm. When there is too much content of a titanium compound, many oligomers will produce | generate at the process of melt-extruding polyester, and the ultraviolet-ray transmittance of the film obtained as a result will fall. Further, when no titanium element is contained, the productivity at the time of production of the polyester raw material is lowered, and a polyester raw material that has reached the desired degree of polymerization cannot be obtained. On the other hand, the amount of phosphorus element needs to be 1 to 300 ppm, preferably 5 to 200 ppm, and more preferably 5 to 100 ppm. When the content of the phosphorus compound is too large, gelation occurs, a large amount of foreign matter is detected, and the ultraviolet transmittance of the film is lowered.

  As a catalyst used for the polymerization reaction, a titanium compound is used for the above reason. In addition, a germanium compound or an antimony compound can be used, but the germanium compound is very expensive and disadvantageous for general use. The antimony compound has an antimony element content of 10 ppm or less in the polyester film. And preferably no antimony element. When the antimony compound is 10 ppm or more, the antimony particles are easily aggregated to become a foreign substance, and when a high-definition circuit pattern is formed, UV transmission is blocked and a defect is caused in the circuit pattern.

  The polyester film referred to in the present invention is a film stretched as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method, which is melt-extruded from an extrusion die.

  As the polyester constituting the polyester film of the present invention, typically, for example, polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6-naphthalate. Specific polyethylene-2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate. Other examples include polyethylene isophthalate and polybutylene terephthalate.

  Examples of copolymer components other than the above-described dominant components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, and polytetramethylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, and 5-sodium dicarboxylic acid. Ester-forming derivatives such as diasulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and oxymonocarboxylic acid can be used. Further, as the polyester, in addition to a homopolymer or a copolymer, a small proportion of a blend with another resin can also be used.

  The polyester film of the present invention needs to contain crosslinked polymer particles having an average particle size of 0.2 to 1.0 μm. The average particle size is preferably in the range of 0.3 to 0.7 μm. When the average particle size is less than 0.2 μm, the winding quality stability of the film is lowered, which is not preferable. On the other hand, when the average particle diameter exceeds 1.0 μm, large protrusions are formed on the film surface, and the ultraviolet transmittance of the film is lowered.

  The particle size distribution (defined later) of the crosslinked polymer particles used in the present invention is 2.0 to 5.0, preferably 2.5 to 4.0. When this value is less than 2.0, it means that the presence of single particles increases, and it becomes difficult to ensure winding quality. On the other hand, if the particle size distribution exceeds 5.0, it means that the presence of large particles increases, and the desired film UV transmittance cannot be obtained.

  The addition amount of the crosslinked polymer particles of the present invention is in the range of 0.01 to 0.15% by weight, preferably 0.03 to 0.10% by weight. If the addition amount is less than 0.01% by weight, the number of particle protrusions formed on the film surface is small, and thus it does not contribute to stabilizing the winding quality. On the other hand, when the addition amount exceeds 0.15% by weight, the desired film can not have the desired ultraviolet transmittance.

  The crosslinked polymer particles used in the present invention can be usually obtained as follows. That is, a compound (a) having only one aliphatic unsaturated bond in the molecule is copolymerized with a compound (b) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent. It is obtained. Examples of the compound (a) which is one component of the copolymer include acrylic acid, crotonic acid, methacrylic acid, and lower alkyl esters such as methyl ester and ethyl ester, or glycidyl ester, maleic anhydride and alkyl thereof. Derivatives, vinyl glycidyl ether, vinyl acetate, acrylonitrile, styrene and substituted products thereof. Examples of the compound (b) include divinylbenzene, ethylene glycol dimethacrylate, butylene glycol acrylate and the like.

  Typical examples of these copolymers include copolymers of methacrylic acid and divinylbenzene, styrene and divinylbenzene, and methacrylic acid and ethylene glycol dimethacrylate. In the present invention, the compound (a ) And (b) may be used to obtain crosslinked polymer particles.

  In the present invention, in order to obtain particles having a specific particle size distribution and average particle size, those obtained directly by suspension polymerization or emulsion polymerization may be blended, but they are easily obtained particularly in the case of suspension polymerization. It is preferable to obtain by pulverizing and classifying a crosslinked polymer having a size of several tens μm to several hundreds μm.

  The film thickness of this invention is 3-16 micrometers normally, Preferably it is 4-12 micrometers, More preferably, it is 4-8 micrometers. If the thickness exceeds 16 μm, light tends to be scattered at the time of exposure and the resolution tends to decrease. If the thickness is less than 3 μm, handling at the time of making the protective tape becomes difficult and workability deteriorates or breaks during peeling. Sometimes.

  The ultraviolet (wavelength 360 nm) transmittance of the polyester film of the present invention is 84% or more, preferably 85% or more. When the ultraviolet transmittance at this wavelength is less than 84%, the exposure and curing steps of the resist layer become inefficient.

  The arithmetic average two-dimensional roughness (Ra) of the polyester film of the present invention is preferably 30 nm or less, and more preferably 20 nm or less. If Ra exceeds 30 nm, the resist layer exposure and curing steps tend to be inefficient.

  Next, a method for producing a polyester film will be described. That is, polyester is melt-extruded from a die of an extruder, cooled and solidified with a casting drum to form an amorphous unstretched film, and stretched in the machine and transverse directions. Stretching in the machine direction is, for example, at a temperature of 70 to 130 ° C. and 3.0 to 5.0 times, preferably 3.5 to 4.5 times. Stretching in the transverse direction is, for example, at a temperature of 70 to 150 ° C., preferably 90 to 140 ° C., and is stretched 3.0 to 5.0 times, preferably 3.5 to 4.5 times in the transverse direction.

  In addition, it is preferable that the heat setting process after extending | stretching of a film is heat-set at the temperature of 150-250 degreeC for the time for 2 to 30 second within the temperature below melting | fusing point higher than final drawing temperature.

  In addition, in order to impart adhesiveness, antistatic ability, and releasability to the film during or after the stretching process, a coating layer is formed on one or both surfaces of the film, or a discharge treatment such as corona treatment is performed. You can also.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the measurement and evaluation method of various physical properties of a film are shown below.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester was accurately weighed and dissolved by adding 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio), and measured at 30 ° C.

(2) Average particle diameter of additive particles (d)
It was measured with a centrifugal sedimentation type particle size distribution analyzer (SP-CP3 type) manufactured by Shimadzu Corporation.
In the present invention, the average particle size is defined as the average particle size (d), which is a particle size with an integrated volume fraction of 50% regardless of the shape.

(3) Size distribution of additive particles (r)
The particle size distribution was determined in the same manner as the average particle size measurement method. Integration was performed from the large particle side in the equivalent sphere distribution, and the particle size distribution ratio (r) was calculated from the following equation.
(R) = particle diameter when particle cumulative weight is 25% / particle diameter when particle cumulative weight is 75%

(4) Measurement of foreign matter inside film Using a FPT-80 type foreign matter detector manufactured by Yachiyo Corporation in a class 100 clean room, the number of foreign matter contained in the film per A4 size (10 μm or more) was measured.

(5) Measurement of film thickness Ten films were stacked, the thickness was measured with a JIS method micrometer, and the average value was obtained by dividing by 10 to obtain the film thickness.

(6) Method for measuring film ultraviolet transmittance The ultraviolet transmittance at a wavelength of 360 nm was measured using a visible ultraviolet spectrophotometer UVIDEC-670 manufactured by JASCO Corporation.

(7) Arithmetic mean two-dimensional roughness (Ra)
It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, the center line of the extracted portion is the x axis, and the direction of the vertical magnification is the y axis. When represented by (x), the value given by the following equation is represented by [μm]. The measurement was performed at 10 points and expressed as an average value. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

(8) Evaluation of the cured state of the resist Photomask protective adhesive tape was prepared for the film by a known method, and a photomask with a linear transmissive part having a width of 20 μm and a linear non-transmissive part having a width of 20 μm arranged in parallel Affixed to the surface facing the resist. This photomask was brought into close contact with a known photoresist, and ultraviolet rays were applied from above at a dose of 300 mJ / cm ² to cure and evaluate the resist.
○: All cured according to photomask pattern ×: Not partially cured according to photomask pattern

(9) Film winding quality stability In the production of a polyester film, the following criteria were used in consideration of the defect rate of the appearance of the product in roll winding of the final product.
○: The occurrence rate of defective products is low and there is no problem in manufacturing. ×: Many defective products are generated, causing problems in manufacturing.

Example 1:
[Production of crosslinked polymer fine powder]
A homogeneous solution of 100 parts of methyl methacrylate, 25 parts of divinylbenzene, 22 parts of ethylvinylbenzene, 1 part of benzoyl peroxide and 100 parts of toluene was dispersed in 700 parts of water. Next, it superposed | polymerized by heating to 80 degreeC, stirring for 8 hours in nitrogen atmosphere. The average particle diameter of the obtained crosslinked polymer granules having ester groups was about 0.1 mm. The granules were washed with demineralized water and extracted three times with 500 parts of toluene to remove a small amount of unreacted monomer and linear polymer. Next, the polymer particles were pulverized with an attritor for 2 hours and further with a sand grinder manufactured by Igarashi Machine Co., Ltd. for 5 hours to obtain a crosslinked polymer fine powder having an average particle size of 0.6 μm. Next, after removing large particles with a super decanter, a crosslinked polymer fine powder having a particle size distribution (r) of 3.1 and an average particle size of 0.5 μm was obtained using a 2400 mesh filter.

<Production of polyester (X1)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, tetrabutoxy titanate as a catalyst is added to the reactor, the reaction start temperature is set to 150 ° C., and the reaction time is gradually increased as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank and subjected to a polycondensation reaction for 4 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding ethyl acid phosphate and crosslinked polymer fine powder to this reaction mixture, it was transferred to a polycondensation tank and subjected to a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.55 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity was 0.55. The obtained polyester chip was subjected to solid phase polymerization at 220 ° C. to obtain polyester (X1) having an intrinsic viscosity of 0.65 and a content of crosslinked polymer fine powder of 0.1% by weight.

<Manufacture of polyester (Y1)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction time is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, and after addition of orthophosphoric acid, a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (Y1) chip. The intrinsic viscosity of the polyester (Y1) was 0.63.

<Film production and resist evaluation>
A raw material obtained by blending 95 parts by weight and 5 parts by weight of a polyester (X1) chip and a polyester (Y1) chip is melt-extruded at a temperature of 290 ° C. using a vented twin-screw extruder, and electrostatically charged. An amorphous film was obtained by casting on a cooling drum while using the adhesion method. This film was stretched 3.8 times in the longitudinal direction at 83 ° C., further stretched 4.0 times in the transverse direction at 110 ° C., and heat treated at 225 ° C. to obtain a polyester film having a thickness of 6 μm. The contents of antimony, titanium, and phosphorus in the obtained film were 0 ppm (below the lower limit of detection), 5 ppm, and 50 ppm, respectively.

  Hereinafter, Tables 3 and 4 collectively show the antimony, titanium, and phosphorus element contents in the films obtained in each Example and Comparative Example, the internal foreign matter and the cured state of the photoresist, and other evaluation results.

Examples 2-4 and Comparative Examples 5-8:
A polyester film was produced in the same manner as in Example 1 except that the particle size distribution (r), average particle size (d), and content of the crosslinked polymer particles were changed.

Examples 5-7:
In the production of polyesters (X1) and (Y1), a polyester film was obtained in the same manner as in Example 1, except that tetrabutoxytitanate, ethyl acid phosphate and normal phosphoric acid were added in different amounts.

Comparative Example 1:
In the production of polyester, Example except that silica particle ethylene glycol slurry having an average particle size of 2.5 μm was added instead of the crosslinked polymer fine powder so that the content of the particles with respect to the polyester was 0.10% by weight. 1 to obtain a polyester (X2) chip having an intrinsic viscosity of 0.66. In Example 1, a polyester film was obtained in the same manner as in Example 1 except that a polyester (X2) chip was used instead of the used polyester (X1) chip.

Comparative Examples 2-3:
In the production of polyesters (X1) and (Y1), a polyester film was obtained in the same manner as in Example 1, except that tetrabutoxytitanate, ethyl acid phosphate and normal phosphoric acid were added in different amounts.

Comparative Example 4:
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction time is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding ethyl acid phosphate to this reaction mixture, it was transferred to a polycondensation tank, and polycondensation reaction was carried out for 4 hours with addition of antimony trioxide. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity of this polyester was 0.63. The obtained polyester chip was subjected to solid phase polymerization at 220 ° C. under vacuum to obtain a polyester film (Z) having an intrinsic viscosity of 0.67. Polyester (Z) was melt-extruded at a temperature of 290 ° C. using a vented twin-screw extruder, and cast on a cooling drum while using an electrostatic adhesion method to obtain an amorphous film. This film was stretched 3.8 times in the longitudinal direction at 83 ° C., further stretched 4.0 times in the transverse direction at 110 ° C., and heat treated at 225 ° C. to obtain a polyester film having a thickness of 6 μm.

  The polyester film of the present invention can be suitably used for, for example, a photomask protective tape.

Claims (1)

The titanium element content in the polyester film is 1 to 20 ppm, the phosphorus element content is 1 to 300 ppm, the antimony element content is 10 ppm or less, the average particle size is 0.2 to 1.0 μm, and the particle size distribution is 2.0. A monolayer polyester film for a photomask protective tape, comprising 0.01 to 0.15% by weight of crosslinked polymer particles of -5.0 and having an ultraviolet transmittance of 84% or more at a wavelength of 360 nm.